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TRACERCO Diagnostics™ - Distribution study

Excess Carryover from a Packed Bed Tower

The examination of packed bed towers by gamma ray scanning is well established but does not always clearly identify the operational problem. A recent project for a major LNG supplier who was experiencing excess carryover from a packed bed tower clearly showed the benefits of the use of tracer technology over gamma scans when applied to packed bed towers

Distribution study

The initial approach was to perform a Tracerco Diagnostic™ Tower scan to look for internal damage and also indications of liquid hold-up or maldistribution. This showed no internal damage or significant maldistribution in the bed.

Further examination utilising a TRACERCO Diagnostics™ Distribution study was then performed. This involved the deployment of 26 detectors around the tower at various elevations both within and above/below the bed.

Both a liquid and then a gas tracer were injected into the individual feed streams to the tower. As these injected “pulses” transited through the tower and bed, a response was obtained at each detector position. Comparisons of these responses are made and these can then be related to the distribution of the phases throughout the tower. The liquid tracer tests showed that there was good distribution throughout the bed in all directions, however the vapour tests showed a serious and very unusual distribution pattern.

Clicking on the following graph shows the results of the vapour distribution tests. This showed little, if any vapour was flowing up the south east quadrant (green trace)

Graphical illustration

Clicking on the graph below shows all of the south east side detectors and this indicates that gas that had travelled up the other sides is now flowing down the south east side rather than continuing up the tower creating a re-circulation effect.

Graphical illustration

The results clearly showed that vapour maldistribution was the cause of the problem. The gamma scans could not detect this and the example highlights the advantages that tracer technology can bring to the examination of packed bed units.

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